1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic printer and an electrophotographic copying machine which form images on recording media.
2. Description of the Related Art
In conventional image forming apparatuses such as a copier and a printer, methods such as an electrostatic recording method and an electrophotographic recording method are used in many cases. Of these methods, there is known a method of transferring a toner image formed on a photosensitive drum to an intermediate transfer member and a recording medium by electrostatic force acting between a transfer roller and the photosensitive drum.
The toner image on the photosensitive drum may not be completely transferred and thus a very small quantity of toner may remain on the photosensitive drum after the toner image is transferred to the recording medium. When charging is caused by bringing a charging device into contact with the photosensitive drum, this remaining toner adheres to the charging device, thereby causing a charging failure. This leads to vertical streaks and uneven density in an image, which is a problem. Therefore, the remaining toner is scraped off and collected by bringing a cleaning blade, which is made of an elastic member, into contact with the photosensitive drum.
However, the cleaning blade may be gradually turned up by a frictional force between the cleaning blade and a surface of the photosensitive drum, and thus become unable to scrape off the remaining toner. In other words, blade turn-up may occur.
There is a configuration in which a functional force between a cleaning blade and a surface of a photosensitive drum is reduced by sending toner into a contact portion between the cleaning blade and the photosensitive drum, as the toner serves as a lubricant.
Even in this case, blade turn-up easily occurs, in particular, at an end part of the cleaning blade in an initial state where a cartridge is installed. This is because, in general, a cleaning blade is disposed to be wider than an image formation region in many cases so that failure to scrape off the toner is prevented, and therefore, the toner sent to the cleaning blade is not easily distributed to an end part of the cleaning blade.
In this connection, one technique is known as follows. In this technique, a lubricant is applied beforehand to a surface, which is to be in contact with a developing roller, of a toner seal member. Such applied agent, which is the lubricant, is supplied to an end part of a cleaning blade via the developing roller and a photosensitive drum, thereby suppressing blade turn-up (Japanese Patent Application Laid-Open No. 2005-181713).
However, when the toner seal member and the end part of the cleaning blade are disposed away from each other in an axial direction of the photosensitive drum, the applied agent may not be sufficiently supplied to the end part of the cleaning blade, which may cause blade turn-up.